Pedal with integrated position sensor

ABSTRACT

A pedal and sensor assembly for mounting to a vehicle. The assembly has a pedal arm having a first end and a second end. A magnetic field generator is connected to the second end to generate a variable magnetic field as the pedal moves. A housing is attached to the vehicle and has the second end and the magnetic field generator contained therein. A magnetic field sensor is located adjacent to the magnetic field generator and detects the variable magnetic field such that as the pedal arm rotates the magnetic field sensor generates an electrical signal proportional to the strength of the variable magnetic field and that is indicative of the position of the pedal arm.

CROSS REFERENCE TO RELATED AND CO-PENDING APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/708,363 filed Nov. 8, 2000 entitled, “Pedal with IntegratedPosition Sensor”, which is a continuation in part of U.S. patentapplication Ser. No. 09/208,296 filed Dec. 9, 1998 entitled, “NonContacting Position Sensor using Bi-polar Tapered Magnets”, and isherein incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] I. Technical Field

[0003] This invention relates, in general, to pedals and pedal sensors.More particularly, this invention relates to a non-contacting positionsensor utilizing Hall effect devices and variable flux fields.

[0004] II. Background Art

[0005] Electronic devices are an increasingly ubiquitous part ofeveryday life. Electronic devices and components are presentlyintegrated in a large number of products, including productstraditionally thought of as primarily mechanical in nature, such asautomobiles. This trend is almost certain to continue. To successfullyintegrate electronic and mechanical components, some type of interfacebetween the two technologies is required. Generally this interface isaccomplished using devices such as sensors and actuators.

[0006] Position sensing is used to electronically monitor the positionor movement of a mechanical component. The position sensor produces anelectrical signal that varies as the position of the component inquestion varies. Electrical position sensors are an important part ofinnumerable products. For example, position sensors allow the status ofvarious automotive parts to be monitored and controlled electronically.A position sensor must be accurate, in that it must give an appropriateelectrical signal based upon the position measured. If inaccurate, aposition sensor will hinder the proper evaluation and control of theposition of the component being monitored. A position sensor must alsobe adequately precise in its measurement. The precision needed inmeasuring a position will obviously vary depending upon the particularcircumstances of use. For some purposes only a rough indication ofposition is necessary, for instance, an indication of whether a valve ismostly open or mostly closed. In other applications more preciseindication of position may be needed.

[0007] A position sensor must also be sufficiently durable for theenvironment in which it is placed. For example, a position sensor usedon an automotive valve will experience almost constant movement whilethe automobile is in operation. Such a position sensor must beconstructed of mechanical and electrical components which are assembledin such a manner as to allow it to remain sufficiently accurate andprecise during its projected lifetime, despite considerable mechanicalvibrations and thermal extremes and gradients.

[0008] In the past, position sensors were typically of the “contact”variety. A contacting position sensor requires physical contact toproduce the electrical signal. Contacting position sensors typicallyconsist of potentiometers to produce electrical signals that vary as afunction of the component's position. Contacting position sensors aregenerally accurate and precise. Unfortunately, the wear due to contactduring movement of contacting position sensors has limited theirdurability. Also, the friction resulting from the contact can result inthe sensor affecting the operation of the component. Further, waterintrusion into a potentiometric sensor can disable the sensor.

[0009] One important advancement in sensor technology has been thedevelopment of non-contacting position sensors. As a generalproposition, a non-contacting position sensor (“NPS”) does not requirephysical contact between the signal generator and the sensing element.As presented here, an NPS utilizes magnets to generate magnetic fieldsthat vary as a function of position and devices to detect varyingmagnetic fields to measure the position of the component to bemonitored. Often, a Hall effect device is used to produce an electricalsignal that is dependent upon the magnitude and polarity of the magneticflux incident upon the device. The Hall effect device may be physicallyattached to the component to be monitored and move relative to thestationary magnets as the component moves. Conversely, the Hall effectdevice may be stationary with the magnets affixed to the component to bemonitored. In either case, the position of the component to be monitoredcan be determined by the electrical signal produced by the Hall effectdevice.

[0010] The use of an NPS presents several distinct advantages over theuse of the contacting position sensor. Because an NPS does not requirephysical contact between the signal generator and the sensing element,there is less physical wear during operation, resulting in greaterdurability of the sensor. The use of an NPS is also advantageous becausethe lack of any physical contact between the items being monitored andthe sensor itself results in reduced drag upon the component by thesensor.

[0011] While the use of an NPS presents several advantages, there arealso several disadvantages that must be overcome in order for an NPS tobe a atisfactory position sensor for many applications. Magneticirregularities or imperfections may compromise the precision andaccuracy of an NPS. The accuracy and precision of an NPS may also beaffected by the numerous mechanical vibrations and perturbations likelybe to experienced by the sensor. Because there is no physical contactbetween the item to be monitored and the sensor, it is possible for themto be knocked out of alignment by such vibrations and perturbations. Amisalignment will result in the measured magnetic field at anyparticular location not being what it would be in the originalalignment. Because the measured magnetic field will be different thanthat when properly aligned the perceived position will be inaccurate.Linearity of magnetic field strength and the resulting signal is also aconcern.

[0012] With the advent of drive by wire systems, also called electronicthrottle control or ETC, a need has developed for accurate and costeffective position sensing of accelerator pedals in automotiveapplications. In particular, an unmet need exists for a non-contactingpedal sensor that has long life and is readily manufacturable.

SUMMARY OF THE INVENTION

[0013] A feature of the invention is to provide a non-contactingposition sensor utilizing Hall effect devices and variable flux fields.

[0014] Another feature of the invention is to provide a pedal and sensorassembly for mounting to a vehicle. The pedal is depressed by a user.The assembly includes a pedal arm having a first end and a second end.The first end is depressed by the user. The pedal arm is rotatable aboutan axis. A magnetic field generator connected to the second end forgenerating a variable magnetic field. A housing is attached to thevehicle and has the second end and the magnetic field generatorcontained therein. The first end emanates from the housing. A magneticfield sensor is located adjacent to the magnetic field generator anddetects the variable magnetic field such that as the pedal arm rotatesthe magnetic field sensor generates an electrical signal proportional tothe strength of the variable magnetic field and is indicative of theposition of the pedal arm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 illustrates an exploded perspective view of a pedalassembly in accordance with the preferred embodiment of the presentinvention.

[0016]FIG. 2 illustrates an enlarged view of the magnet assembly fromFIG. 1.

[0017]FIG. 3 illustrates a cross sectional side view of the pedalassembly in an assembled state.

[0018]FIG. 4 illustrates an end view of the pedal assembly in anassembled state.

[0019] It is noted that the drawings of the invention are not to scale.The drawings are intended to depict only typical embodiments of theinvention, and therefore should not be considered as limiting the scopeof the invention. The invention will be described with additionalspecificity and detail through the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] Referring to FIGS. 1, 2, 3 and 4, a Pedal Position Sensor UsingBipolar Tapered Magnets is shown. Pedal and sensor assembly 10 includesa housing 20. Housing 20 has a cavity 21, connector opening 22, pedalopening 23 and inner wall 29. A rod aperture 24 passes through housing20. Several bulkhead mounting holes 25 are located on back wall 30. Backwall 30 is designed to be placed against a bulkhead in a vehicle andsecured to the bulkhead with bolts (not shown) that pass through holes25. A rectangular connector plate 26 is mounted over connector opening22 and is ultrasonically welded or heat staked to housing 20. Aconnector shroud 27 extends outwardly from connector plate 26. A wireharness connector (not shown) mates with connector shroud 26 to providean electrical connection from assembly 10 to an external electroniccircuit such as a computer in the vehicle. Connector plate 26 also has acircuit board retainer 28 extending into cavity 21. Housing 20 ispreferably formed from injection molded plastic.

[0021] An elongated pedal arm 40 has a first end 41 and a second end 42.A rubber foot rest 43 is attached or molded to first end 41. Pedal arm40 is preferably formed out of injected molded plastic. Footrest 43 isdepressed by the foot of a user during use in a vehicle. A pair offlanges 45 that extend outwardly on each side of second end 42. Abushing 59 passes through flanges 45 and end 42. A rod aperture 44passes through flanges 45. Magnet projection 47 and friction plateprojection 50 extend from second end 42. Magnet projection 47 has arecess 48 therein and a magnet mounting aperture 49 passing through.Projection 47 has a lip 46 extending upwardly to assisting in retentionof the magnets. Alternatively, Friction plate projection 50 has afriction plate aperture 51 passing therethrough. A steel friction platepin 53 is mounted into aperture 51 and extends on each side of end 42.Friction plates 52 slide over pin 53. The friction plates rub againstwall 29 to provide a hysteresis feel. That is increasing resistance asthe pedal is depressed and a reduction in force as the pedal returns. Apair of steel coil springs 54 are mounted over flanges 45. Springs 54have one end that rests on friction plate 52 and another end that isheld inside cavity 21. Spring 54 returns pedal arm 40 to a startingposition when the pedal is not being depressed. A steel rod 56 passesthrough apertures 24 and 44 along axis of rotation 58, in order toretain the pedal arm 40 in housing 20. Snap rings 57 attach over ends ofrod 56 to retain rod 56 in place.

[0022] Magnet assembly or magnetic field generator 60 includes a pair ofmagnetically permeable pole pieces 64 and a pair of tapered magnets 62.

[0023] The pole pieces 64 are bonded to magnets 62. The magnet and polepieces have a projection 66 that fits within recess 66. Lip 46 extendsupwardly from projection 47 and assists in retaining magnets 62. Each ofthe magnets and pole pieces 62 and 64 straddle the projection 47 and areheld there by a fastener (not shown) that passes through aperture 49.Alternatively, the magnets may be integrally injection molded into thepedal arm eliminating the need for a fastener. An air gap 68 is formedby the magnets 62 being held apart. The pole pieces are preferablyformed from sheets of magnetically permeable material such as stainlesssteel. The magnets typically are polymer ferrite magnets. Circuit board70 mounts into circuit board retainer 28 and has one or more magneticfield sensors such as a hall effect device 72 mounted thereon. Terminals74 are connected to circuit board 70 and extend into shroud 27. The halleffect device 72 is mounted in the air gap 68. The description andoperation of magnetic field generator 60 is described in detail in U.S.patent application Ser. No. 09/208,296 filed Dec. 9, 1998 entitled, “NonContacting Position Sensor using Bi-polar Tapered Magnets”, which isincorporated by reference in entirety.

[0024] Pedal and sensor assembly 10 detects rotary motion of the pedalas it is depressed by the foot of a user. The Hall effect device 72 andcircuit board 70 are stationary while the magnets 62 rotate about axis58. The circuit board may be attached to the retainer 28 using heatstaking or similar methods. The circuit board 70 also carries electroniccircuitry for processing signals from the hall effect devices. The halleffect device 72 is electrically connected to the terminals 74. Theelectrical terminals 74 are designed for interconnection with a standardmating connector. As the magnetic field generated by the magnetic fieldgenerator 60 varies with rotation about axis 58, the signal produced bythe Hall effect device 72 changes linearly, allowing the position of thepedal to be monitored to be ascertained. In other words, the magneticfield sensor detects the variable magnetic field such that as the pedalarm rotates the magnetic field sensor generates an electrical signalproportional to the strength of the variable magnetic field that isindicative of the position of the pedal arm.

[0025] Pedal and sensor assembly 10 is assembled in the followingmanner. Tube 59 and pin 53 are pressed into their respective aperturesin second end 42. Each half of magnet 62 and pole piece 64 are place onopposite sides of magnet projection 47 with projection 66 fitting intorecess 48. Fasteners (not shown) pass through magnet aperture 49 toretain the magnets and pole pieces. Next, the friction plates 52 areslid over pin 53 and springs 54 are placed over flanges 45. The pedalarm 40 is next slid into pedal opening 23 and rod 56 is slid throughapertures 24 and 44 to retain the pedal arm to the housing. Snap rings57 are attached to rod 56 to retain rod 56. Circuit board 70 is slidinto circuit board retainer 28. Circuit board retainer 28 has tabs (notshown) that hold the circuit board 70. Connector plate 26 is placed overconnector opening 22 and ultrasonically welded or heat staked to housing20 completing the assembly. Alternatively, the magnets may be integrallyinjection molded into the pedal arm eliminating the need for a fastener.One skilled in the art will likewise readily ascertain other variationsthat may easily be made without departing from the spirit and scope ofthe present invention.

What is claimed is:
 1. A pedal and sensor assembly for mounting to avehicle, the pedal being depressed by a user, comprising: a) a pedal armhaving a first end, a second end and an aperture; b) a rod extendingthrough the aperture; c) a magnetic field generator connected to thesecond end for generating a magnetic field; d) a housing, attachable tothe vehicle and rotatably supporting the rod; and e) a magnetic fieldsensor disposed adjacent the magnetic field generator for detecting themagnetic field.
 2. The pedal and sensor assembly according to claim 1wherein the magnetic field generator is a permanent magnet.
 3. The pedaland sensor assembly according to claim 2, wherein the magnet is tapered.4. The pedal and sensor assembly according to claim 3, wherein themagnetic field sensor is a hall effect device.
 5. The pedal and sensorassembly according to claim 4, wherein the second end has a frictionplate attached for engagement with a wall of the housing to provide aresistive feedback to the user.
 6. The pedal and sensor assemblyaccording to claim 5, wherein the second end has a pair of flanges oneach side of the second end, the flanges each having a coil springmounted thereon.
 7. A pedal and sensor assembly for mounting to avehicle, the pedal being depressed by a user, comprising: a) a pedal armhaving a first end, a second end and a pair of flanges extendingoutwardly from the pedal arm, the first end adapted to be depressed bythe user; b) a housing, attachable to the vehicle, the housing rotatablysupporting the pedal through the flanges; c) a magnetic field generatorattached to the second end of the pedal arm for generating a magneticfield, the magnetic field generator moving as the second end moves; andd) a magnetic field sensor mounted to the housing, adjacent the magneticfield generator for detecting the magnetic field such that as the pedalarm rotates the magnetic field sensor generates an electrical signalproportional to the strength of the magnetic field and indicative of theposition of the pedal arm.
 8. The pedal and sensor assembly according toclaim 7 wherein the magnetic field generator is a permanent magnet. 9.The pedal and sensor assembly according to claim 8, wherein the magnetgenerates a variable magnetic field.
 10. The pedal and sensor assemblyaccording to claim 7, wherein the magnetic field sensor is a hall effectdevice.
 11. The pedal and sensor assembly according to claim 7, whereinthe housing has an aperture extending through the housing, a rod mountedthrough the aperture and the flanges.
 12. The pedal and sensor assemblyaccording to claim 7, wherein the flanges each having a coil springmounted thereon.